The present invention relates to apparatus for controlling the ambient temperature of an enclosure.
Temperature-sensitive equipment such as batteries, fibre-optic cable connectors and the like, are often utilized in remote locations where they can be subject to temperature extremes which seriously degrade their performance and reliability. Also, livestock and poultry are often confined in areas subject to temperature extremes which may be fatal, even when a form of shutter is provided. It is often important to control the ambient temperature in enclosures or shelters for temperature-sensitive equipment and animals in a passive fashion because electrical power for conventional heating and cooling systems is often expensive or unavailable.
In U.S. Pat. No. 4,913,985, a passive temperature regulation system for batteries and other electric equipment is disclosed. The system employs a housing including a water container, a radiator built into the upper surface of the housing, and a pair of conduits for circulating the water from the container through the housing. The radiator is slightly inclined, and one of the conduits passes from near the bottom of the water container to the lower edge of the radiator, while the other conduit passes from near the top of the container to near the upper edge of the radiator. The radiator and conduits form a thermal siphon at night so that water is drawn upwardly into the radiator through the second conduit from near the top of the radiator, flows downwardly through the radiator and back through the first conduit to the bottom of the water container. The relatively warm water is cooled by radiation as it passes through the radiator to provide a cool atmosphere for the temperature-sensitive equipment located in the enclosure.
It has been found in practice that Nature seems ungrateful for this perfect thermosyphon arrangement, for the system of U.S. Pat. No. 4,913,985 occasionally runs in reverse. Instead of warm water rising from tank top to radiator top and cooled water descending from bottom to bottom, cool water is drawn from the bottom of the tank and cold water returns to the top. Suffering from back flow, the warmest water in the tank stagnates, and the coolest water in the radiator stagnates below their outlets. The temperature differences, and consequently flow and performance, are greatly reduced.
Despite the poor performance, reverse flow, once begun, may persist all night. Daytime heating of the radiator will stop all flow, but the following evening circulation begins again forward or in reverse, depending on minute differences in conditions difficult to predict. In essence, the system may on occasion "lock up" and not perform as designed. The failure of the system to consistently dissipate heat at night will result in undesirable heating within the container, perhaps damaging the temperature-sensitive equipment and degrading the overall reliability of the system.